Sorting devices of the kind described above have been know for a long time as cell sorting devices, for example, those distributed by the Becton Dickinson Company in different models. In these known cell sorters, an optical and electronic evaluation unit is used for particle analysis. Therein, the sorting stream flows through one or several laser light beams. The light, which is scattered by the cells to be sorted, or the fluorescence signals coming out of them are observed and analyzed by the optical evaluation unit.
In the sorting method mentioned above, drops within the order of magnitude of 40-200 μm and satellite drops with diameters within the range of 3-7 μm are formed. If these drops hit against collection receptacles or against objects, droplet splashes and particulate matter of different sizes are formed. While the drops with a diameter greater than 80 μm settle relatively fast from the air, smaller drops can remain suspended for a long time (especially by means of currents) in the air as particulate matter. This particulate matter is only partially drawn off, while a protective wall is provided between the point of origin of these fine droplets, particulate matter, and the operator. In a cell sorting device with an additional protective device pursuant to WO 0185088 A1, the particulate matter is drawn off upward out of a safety chamber and is retained by means of a HEPA filter. The safety housing, which initially does not have a rear wall, is positioned in this system over the front face of a cell sorter and is sealingly connected thereto at the peripheral edge of its rear side. It was discovered that these safety measures are not always sufficient, for example, when the substances to be sorted are eventually toxic substances and/or biohazardous materials, for whose handling have to be ensured higher safety standards. Just like with the personnel protection, a special protection is simultaneously required furthermore in an increasing number of applications in order to protect, for example, lymphocytes or stem cells from contamination and/or to sort genetically modified organisms according to the specifications of the Genetic Engineering Law.
U.S. Pat. No. 6,780,277 B2 discloses an environment protection system with the object of both protecting the particles treated in the flow cytometer from contaminants as well as also protect the operators of the flow cytometer from the particles to be treated. For this purpose, some parts of a flow cytometer are arranged inside of a housing, while other parts, for example, the evaluation units, can be provided on the outside of the housing. The detector system and other monitoring means can likewise be arranged outside of the housing. A throughflow system is also provided for the housing in order to maintain a specific gas atmosphere within the housing.—A system such as this is neither suitable nor safe enough for the practical laboratory activity or economic recovery of particles to be protected and/or potentially hazardous particles.